Kinetics and mechanism of the homogeneous oxidation of quinaldine red by hydrogen peroxide

The kinetics of the oxidation of quinaldine red, a cationic dye, using hydr ogen peroxide has been studied in aqueous solution, The rate of reaction wa s found to be first order in [quinaldine red] whereas in hydrogen peroxide it varies from one to zero with increasing [H2O2]. The rate of reaction inc reases with increasing pH as well as with the addition of sodium carbonate. The reaction rate attains a limiting value at higher carbonate concentrati ons which is attributed to the maximum formation ol peroxide anions. The ra te of hydrogen peroxide decomposition in the presence of sodium carbonate i s much greater than that of bleaching of the dye under the same conditions. Moreover, the rate of reaction decreases with increasing ionic strength su ggesting an interaction between two singly oppositely charged ions in the a ctivated complex. A plausible reaction mechanism is proposed with a rate eq uation that is in agreement with the experimental data.